The present invention, in some embodiments thereof, relates to a system and method of injecting current into a body, measuring electric potential at a surface of the body, and using a model of the body to calculate bone dielectric properties for diagnosis and monitoring of Osteoporosis, and more particularly, but not exclusively, to using Electrical Impedance Tomography (EIT) for diagnosis and monitoring of Osteoporosis.
Osteoporosis is a disease in which density and quality of bones is reduced, leading to a weakness of the skeleton and to an increased risk of fracture, particularly of the spine, wrist and hip. Osteoporosis occurs when a body fails to form enough new bone. Osteoporosis and associated fractures are an important cause of mortality and morbidity. Osteoporosis is a global problem which is increasing in significance as the population of the world both grows and ages. Worldwide, lifetime risk for osteoporotic fractures in women is 30-50%. In men, the risk is 15-30%. There are three main types of Osteoporosis fractures: (1) Wrist fracture, (2) Vertebral fracture and (3) Hip fracture.
Since bone loss occurs without symptoms, there are no symptoms in the early stages of Osteoporosis and it's often called the “silent disease”. In many cases the first symptom is a broken bone! Patients with Osteoporosis may not know that they have the disease until their bones become so weak that a sudden strain, bump, or fall causes a hip fracture or a vertebra to collapse. Collapsed vertebra may initially be felt or seen in the form of severe back pain, loss of height, or spinal deformities such as kyphosis, or a severely stooped posture.
Researchers estimate that about 1 out of 3 women over the age of 50 will suffer a fracture due to Osteoporosis. About half of all women over the age of 60 will have a fracture of the hip, wrist, or vertebra (bones of the spine). Once a woman suffers a first vertebral fracture, there is a five-fold increase in the risk of developing a new fracture within one year.
Approximately, 1.6 million hip fractures occur each year worldwide. The highest risk of hip fractures is seen in Norway, Sweden, Iceland, Denmark and the USA. Currently, there is an increasing incidence of hip fractures in developed cities in Asia. 1 out of 4 hip fractures occur in Asia and Latin America. In the Middle East, the burden of Osteoporosis in the general population is expected to increase and is becoming a heavy financial burden.
According to WHO, Osteoporosis is second only to cardiovascular disease as a global healthcare problem and medical studies show a 50-year-old woman has a similar lifetime risk of dying from hip fracture as from breast cancer. Since Osteoporosis affects the elderly population which is growing, it will put a bigger burden to the healthcare system, as treatment of Osteoporosis is expensive. Unless swift action is taken, Osteoporosis can escalate into an economic threat. The International Osteoporosis Foundation (IOF) estimates that the annual direct cost of treating Osteoporosis fractures of people in the workplace in the USA, Canada and Europe alone is approximately 48 billion USD. The worldwide cost burden of Osteoporosis (for all ages) is forecast to increase to 131.5 billion USD by 2050. Osteoporosis also results in huge indirect costs that are rarely calculated and which are probably at least 20% of the direct costs.
The annual incidence rate of osteoporotic fractures in women is greater than the combined incidence rates of heart attack, stroke and breast cancer.
An article titled “Induced Current Bio-impedance Technique for Monitoring Bone Mineral Density—A Simulation Model”, by Sagie Katz, Sharon Zlochiver, and Shimon Abboud (the present inventor) published in Annals of Biomedical Engineering, Vol. 34, No. 8, August 2006, pp. 1332-1342, describes a feasibility study of using an induced current bio-impedance technique as a method to determine and monitor bone mineral density (BMD). BMD was theoretically evaluated using a computerized simulation model. A 2D polar coordinate numerical solver was developed using the Finite Volume Method (FVM) in order to simulate developed potentials over an axial CT cross section of a human thigh. Varying femur BMDs were simulated by varying femur relative permittivity values. At a chosen excitation current of 1 ampere at a frequency of 20 kHz, the real component of the surface potential was found to be more sensitive to BMD variation than the imaginary component (3.9 μVg-1 cm3 compared with 0.174 μVg-1 cm3).
A correlation between varying femur permittivity values and a real component of a developed surface potential was found to be quadratic, and influenced by coil geometry and measuring point location. Measurement sensitivity was improved either by taking the measuring point to be closer to the femur location or by minimizing the distance between the excitation coil and the femur.
Additional background art relating to measurement of volume of chest organs using EIT includes:    U.S. Published patent application number 2012/0150050 of Arad;    U.S. Pat. No. 8,131,354 of Arad;    U.S. Pat. No. 7,907,998 of Arad; and    U.S. Pat. No. 7,096,061 of Arad.
Additional background art includes:    An article titled “The dielectric properties of biological tissues: I. Literature Survey”, by C. Gabriel, S. Gabriely and E. Corthout, published in Phys. Med. Biol. 41 (1996) 2231-2249.    An article titled “Parametric EIT vs. intra-thoracic impedance for monitoring pulmonary edema using a two dimensional theoretical model of the thorax” by Keren Horman and Shimon Abboud, published in Int. J. Medical Engineering and Informatics, Vol. 5, No. 2, 2013.    An article titled “Assessment of cardiac stroke volume in patients with implanted cardiac pacemaker using parametric electrical impedance tomography: A theoretical 2D study” by Muhammad Mhajna and Shimon Abboud, published in International Journal For Numerical Methods In Biomedical Engineering 2013; 29:630-640, and also published online 19 Apr. 2013 in Wiley Online Library (wileyonlinelibrary(dot)com). DOI: 10.1002/cnm.2550.    A white paper by titled “Sunlight—The Multi-Site Advantage”, by a company named BeamMed Ltd., of 8 Ha-Lapid St., P.O Box 7520, Petah Tikva 49170, Israel, which describes a multi-site bone sonometer (ultrasound bone density measurement system).    An article titled “Monitoring lung fluid content in CHF patients under intravenous diuretics treatment using bio-impedance measurements” by D Freimark, M Arad, R Sokolover, S Zlochiver and S Abboud, in Physiol. Meas. 28 (2007) S269-S277 doi:10.1088/0967-3334/28/7/S20.    An article titled “Monitoring Lung Resistivity Changes in Congestive Heart Failure Patients Using the Bioimpedance technique”, by Sharon Zlochiver, Michal M. Radai, Deganit Barak-Shinar, Tuvia Ben-Gal, Vicky Yaari, Boris Strasberg, and Shimon Abboud, published in Congestive Heart Failure® November December 2005.    An article titled “A portable bio-impedance system for monitoring lung resistivity” by S. Zlochiver, M. Arad, M. M. Radai, D. Barak-Shinar, H. Krief, T. Engelman, R. Ben-Yehuda, A. Adunsky and S. Abboud, in Medical Engineering & Physics 29 (2007) 93-100.    An article titled “The detection of pleural effusion using a parametric EIT technique” by M Arad, S Zlochiver, T Davidson, Y Shoenfeld, A Adunsky and S Abboud, in Physiol. Meas. 30 (2009) 421-428.    An article titled “A Novel Telemedicine System for Monitoring Congestive Heart Failure Patients”, by Michal M Radai, Marina Arad, Sharon Zlochiver, Haim Krief, Tzvika Engelman and Shimon Abboud, in telemedicine for CHF patients, September October 2008.    An article titled “Estimating pulmonary congestion in elderly patients using bio-impedance technique: Correlation with clinical examination and X-ray results” by Marina Arad, Sharon Zlochiver, Tina Davidson, Ora Shovman, Yehuda Shoenfeld, Avraham Adunsky and Shimon Abboud, in Medical Engineering & Physics 31 (2009) 959-963.    An article titled “Parametric EIT for monitoring cardiac stroke volume” by S Zlochiver, D Freimark, M Arad, A Adunsky and S Abboud, in Physiol. Meas. 27 (2006) S139-S146.    An article titled “Diagnosis of elderly pneumonia patients using a parametric electrical impedance tomography system—a preliminary study” by M. Arad, A. Adunsky, S. Zlochiver, S. Abboud and T. Davidson, in Int. J. Medical Engineering and Informatics, Vol. 2, No. 4, 2010.    An article titled “The Electrical and Dielectric Properties of Human Bone Tissue and Their Relationship with Density and Bone Mineral Content” by Paul Allen Williams and Subrata Saha, published in Annals of Biomedical Engineering, Vol. 24, pp. 222-233, 1996.
The disclosures of all references mentioned above and throughout the present specification, as well as the disclosures of all references mentioned in those references, are hereby incorporated herein by reference.